[lld/ELF] Add --override-section-flags flag

lld/ELF/Config.h

@@ -309,6 +309,8 @@ struct Config {
   bool optEL = false;
   bool optimizeBBJumps;
   bool optRemarksWithHotness;
+  llvm::SmallVector<std::tuple<llvm::GlobPattern, uint32_t>, 0>
+      overrideSectionFlags;
   bool picThunk;
   bool pie;
   bool printGcSections;

lld/ELF/Driver.cpp

@@ -1611,6 +1611,35 @@ static void readConfigs(Ctx &ctx, opt::InputArgList &args) {
     }
   }
 
+  for (opt::Arg *arg : args.filtered(OPT_override_section_flags)) {
+    SmallVector<StringRef, 0> fields;
+    StringRef(arg->getValue()).split(fields, '=');
+    if (fields.size() != 2) {
+      error(arg->getSpelling() +
+            ": parse error, no '=' found in --override-section-flags arg");
+      continue;
+    }
+
+    uint32_t flags = 0;
+    for (char c : fields[1]) {
+      if (c == 'a')
+        flags |= SHF_ALLOC;
+      else if (c == 'w')
+        flags |= SHF_WRITE;
+      else if (c == 'x')
+        flags |= SHF_EXECINSTR;
+      else
+        error(arg->getSpelling() + ": flags do not match [awx]+");
+    }
+
+    if (Expected<GlobPattern> pat = GlobPattern::create(fields[0])) {
+      config->overrideSectionFlags.emplace_back(std::move(*pat), flags);
+    } else {
+      error(arg->getSpelling() + ": " + toString(pat.takeError()));
+      continue;
+    }
+  }
+
   for (opt::Arg *arg : args.filtered(OPT_z)) {
     std::pair<StringRef, StringRef> option =
         StringRef(arg->getValue()).split('=');

lld/ELF/InputSection.cpp

@@ -47,13 +47,21 @@ static ArrayRef<uint8_t> getSectionContents(ObjFile<ELFT> &file,
   return check(file.getObj().getSectionContents(hdr));
 }
 
+uint32_t effectiveSectionFlags(uint32_t flags, StringRef name) {
+  for (auto &[glob, overriddenFlags] : config->overrideSectionFlags) {
+    if (glob.match(name))
+      return overriddenFlags;
+  }
+  return flags;
+}
+
 InputSectionBase::InputSectionBase(InputFile *file, uint64_t flags,
                                    uint32_t type, uint64_t entsize,
                                    uint32_t link, uint32_t info,
                                    uint32_t addralign, ArrayRef<uint8_t> data,
                                    StringRef name, Kind sectionKind)
-    : SectionBase(sectionKind, name, flags, entsize, addralign, type, info,
-                  link),
+    : SectionBase(sectionKind, name, effectiveSectionFlags(flags, name),
+                  entsize, addralign, type, info, link),
       file(file), content_(data.data()), size(data.size()) {
   // In order to reduce memory allocation, we assume that mergeable
   // sections are smaller than 4 GiB, which is not an unreasonable

lld/ELF/Options.td

@@ -353,6 +353,10 @@ def omagic: FF<"omagic">, MetaVarName<"<magic>">,
 defm orphan_handling:
   Eq<"orphan-handling", "Control how orphan sections are handled when linker script used">;
 
+defm override_section_flags:
+  EEq<"override-section-flags", "Override section flags">,
+  MetaVarName<"<section-glob>=[awx]+">;
+
 defm pack_dyn_relocs:
   EEq<"pack-dyn-relocs", "Pack dynamic relocations in the given format">,
   MetaVarName<"[none,android,relr,android+relr]">;

lld/test/ELF/override-section-flags.s

@@ -0,0 +1,38 @@
+# REQUIRES: x86
+
+# RUN: rm -rf %t && mkdir %t
+# RUN: llvm-mc -filetype=obj -triple=x86_64 %s -o %t/a.o
+
+# RUN: ld.lld -pie %t/a.o -o %t/out \
+# RUN:     --override-section-flags 'foo0=' \
+# RUN:     --override-section-flags 'foo1=a' \
+# RUN:     --override-section-flags 'foo2=ax' \
+# RUN:     --override-section-flags 'foo3=aw' \
+# RUN:     --override-section-flags 'foo4=awx'
+
+# RUN: llvm-readelf --sections --segments %t/out | FileCheck %s
+
+# CHECK-DAG: foo0 PROGBITS {{[0-9a-f]+}} {{[0-9a-f]+}} {{[0-9a-f]+}} {{[0-9a-f]+}}     {{[0-9a-f]+}} {{[0-9a-f]+}} {{[0-9a-f]+}}
+# CHECK-DAG: foo1 PROGBITS {{[0-9a-f]+}} {{[0-9a-f]+}} {{[0-9a-f]+}} {{[0-9a-f]+}} A   {{[0-9a-f]+}} {{[0-9a-f]+}} {{[0-9a-f]+}}
+# CHECK-DAG: foo2 PROGBITS {{[0-9a-f]+}} {{[0-9a-f]+}} {{[0-9a-f]+}} {{[0-9a-f]+}} AX  {{[0-9a-f]+}} {{[0-9a-f]+}} {{[0-9a-f]+}}
+# CHECK-DAG: foo3 PROGBITS {{[0-9a-f]+}} {{[0-9a-f]+}} {{[0-9a-f]+}} {{[0-9a-f]+}} WA  {{[0-9a-f]+}} {{[0-9a-f]+}} {{[0-9a-f]+}}
+# CHECK-DAG: foo4 PROGBITS {{[0-9a-f]+}} {{[0-9a-f]+}} {{[0-9a-f]+}} {{[0-9a-f]+}} WAX {{[0-9a-f]+}} {{[0-9a-f]+}} {{[0-9a-f]+}}
+
+
+.globl _start
+_start:
+
+.section foo0,"aw"
+.space 8
+
+.section foo1,"aw"
+.space 8
+
+.section foo2,"aw"
+.space 8
+
+.section foo3,"ax"
+.space 8
+
+.section foo4,"a"
+.space 8